Myocardial perfusion reserve quantification by CZT-SPECT: a head to head comparison with Rubidium-82 PET

Objectives: Noninvasive evaluation of myocardial perfusion reserve (MPR) represents a valid tool to increase the diagnostic and prognostic value of myocardial perfusion imaging (MPI). Positron emission computed tomography (PET)/computed tomography (CT) is the gold standard for non-invasive evaluation of MPR; however, quantification of MBF and MPR by dynamic ^99mTc-sestamibi CZT-SPECT is technically feasible. Aim of the present study was to evaluate MBF and MPR assessed by dynamic CZT-SPECT and ⁸²Rb PET/CT in a cohort of patients with suspected or known coronary artery disease (CAD) and available coronary angiography data and to investigate the accuracy of dynamic data in predicting obstructive CAD.

Methods: We analyzed 25 patients (19 men, mean age 61±13 years) with suspected or known CAD. All patients underwent rest-stress by ^99mTc-sestamibi CZT-SPECT and ⁸²Rb PET/CT. Stress and rest MBF and MPR were calculated by both methods and compared. Diagnostic accuracy of MPR by both SPECT and PET imaging were assessed using a receiver-operator-characteristic curve.

Results: CZT-SPECT yielded similar baseline MBF, but higher stress MBF and MPR values as compared to PET. There was a modest correlation between CZT-SPECT and PET for global MPR (r = 0.56, P <0.01). At ROC curve analysis, global MPR by CZT-SPECT showed a good ability in identifying a reduced MPR by PET, with AUC of 0.85. A MPR cut-off of 2.5 was identified by CZT-SPECT for detection of abnormal MPR by PET, with a sensitivity, specificity and accuracy of 86%, 73%, and 80%, respectively. The AUCs at ROC analysis for the identification of obstructive CAD by regional MPR were 0.83 for CZT-SPECT and 0.84 for PET, respectively (P = 0.90) (Fig. 4). At CZT-SPECT, a regional MPR of 2.07 provided the best trade-off between sensitivity and specificity for identifying obstructive CAD. Diagnostic performance of CZT-SPECT and PET using respective cut-off values was comparable.

Conclusions: Hyperemic MBF and MPR values obtained by CZT-SPECT were higher as compared to ⁸²Rb PET, with a modest correlation between the two methods. A high diagnostic value of MPR by CZT-SPECT in identifying abnormal MPR by PET and a similar accuracy of the two methods to identify obstructive CAD at coronary angiography may encourage the use of this new technique to a better risk stratification and patient management.